Update MultipartRequestHandler.java

[rezgui]

convert byte size into human readable format

                                   SI     BINARY

                           0:        0 B        0 B
                         27:       27 B       27 B
                        999:      999 B      999 B
                      1000:     1.0 kB     1000 B
                       1023:     1.0 kB     1023 B
                       1024:     1.0 kB    1.0 KiB
                        1728:     1.7 kB    1.7 KiB
                    110592:   110.6 kB  108.0 KiB
                   7077888:     7.1 MB    6.8 MiB
                452984832:   453.0 MB  432.0 MiB
             28991029248:    29.0 GB   27.0 GiB
         1855425871872:     1.9 TB    1.7 TiB

9223372036854775807: 9.2 EB 8.0 EiB (Long.MAX_VALUE)